Industrial wipes are disposable non oven products used for a variety of applications in industry and institutions, including food service wipes, general industrial, specialty wipes and medical wipes. These products can be wet or dry and may be impregnated with ingredients for specific purposes, such as polishing, cleaning, or removing bacteria. As a result of the desire for convenient, time saving, easy to use products that are economically efficient and prevent cross-contamination there is an ongoing need for single or limited-use industrial and institutional wipes which meet the performance and economy sought by the target end use and processes to produce them which are economical and energy efficient.
Nonwoven wipes, whether intended for consumer application or industrial application may be engineered to provide products of high strength, good abrasion resistance and good hygiene which have no residual oils or contaminants such as heavy metals. Utilities for an industrial wipe may include cleaning machinery, tools, floors and facilities, absorbing fluids and oil, personal cleaning and hygiene, polishing and dust removal.
Conventionally, nonwoven disposable wipe products have been produced through a wide range of industrial methods which are known to one of skill in the art. Generally, although each manufacturer employs technical variation in order to obtain nonwoven webs of specific target properties, the conventionally most common methods employed may be categorized broadly by the terms airlaid, spunlacing, double recrepe, airlacing and hydroentangled co-form.
Basic airlaid webs are composed of fibers dry laid on a forming web. In order to obtain strength most airlaid nonwovens are bonded with latex binder compositions or multibonded with bicomponent adhesive fibers and latex. Airlaid webs may offer advantage by use of low cost and biodegradable raw material (wood pulp), but also include non-biodegradable and expensive latex binder and bicomponent fibers. As a result, depending on the binder and/or bicomponent fiber content the nonwoven may be stiff or have only moderate dry/wet strength and abrasion resistance.
According to the “hydraspun” method as described in U.S. Pat. No. 4,755,421 to Manning et al. a wetlaid web of pulp and manmade fibers is hydroentangled in a spunlacing operation and dried. However, such products may suffer from poor wet strength which is typically compensated with the addition of non-biodegradable binders. U.S. Pat. No. 7,732,357 to Annis et al. describes the use of binder fibers to the nonwoven sheet that upon heating become activated by at least partial melting and form fiber to fiber bonds. Accordingly, depending on the fiber composition which may generally contain a high content of staple manmade fiber and bicomponent fiber, spunlace webs may be expensive or if bonding fibers are not present or of low content the nonwoven web may suffer from low strength, low abrasion resistance and poor dimensional stability.
In a double recrepe process (DRC), a base sheet is creped, then printed with a latex binder on one side of the base sheet. The printed base sheet is creped again, then printed with a binder on the other side of the base sheet, followed by creping the base sheet a third time. The DRC process provides a web possessing a good combination of strength and softness, but has lower strength, and abrasion resistance and includes a non-biodegradable latex binder.
Airlace methods generally include a combination of air-layering and then spunlacing the web. Conventionally, a precursor or base nonwoven web of staple manmade fibers is first produced, then an airlaid web of pulp fibers is deposited on it. The two webs are entangled in the spunlacing operation.
Airlace methods combine the operations of depositing an airlaid web of staple length fibers and wood pulp fibers onto a nonwoven carrier layer or precursor base nonwoven web and hydroentangling the airlaid layer with the nonwoven carrier. This technology is described in U.S. Pat. No. 8,250,719 to Ouellette and the references described therein. In addition to employing a carrier web, Ouellette describes bonding the airlaid fibers with hot air or a spray adhesive.
Hydroentangled co-formed webs are prepared by preforming at least two fibrous layers and hydroentangling the layers. The components of the co-formed mixture generally include wood pulp and thermoplastic filaments.
There remains a need for a method to prepare a nonwoven web suitable for use as an industrial wipe that has good dry/wet strength properties, high absorbency, low or no lint or dust content and having a good feel to the user.
Thus, an objective of the present invention is to provide a method to produce a nonwoven web that includes minimal processing operations, does not use adhesives or binders and provides a nonwoven web having sufficient wet tensile strength and absorbency for use as an industrial wipe. Another objective of this invention is to provide a nonwoven web having sufficient wet strength and absorbency to be employed as an industrial wipe.